In conventional internal combustion engines, control of the air/fuel ratio combusted by the engine during transient operation is typically achieved by measuring the mass flow rate of air into the intake manifold and generating an air flow value which is indicative of the air charge entering the cylinders of the engine per intake event. The correct amount of fuel to be injected for stoichiometric operation is then determined based on the air flow value and additional corrections for fuel wall wetting phenomena.
The primary impediment to accurate air/fuel control during transient operation is the accuracy of the air flow and fuel flow calculations. Moreover, even if the air flow and fuel flow calculations are correct for a particular vehicle, they may not be applicable for other vehicles due to vehicle-to-vehicle variation. In addition, aging of the vehicle causes further changes which affect the fuel and air flow rates. Conventional systems fail to account for such variations during transient engine operation because the control systems contain no mechanisms for measuring the accuracy of the air and fuel flow calculations. Accordingly, performance suffers and emissions increase during transient engine operation.